Lithium Titanate Negative Electrode Reducing CO2 Generation

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Solution Overview

Problem

Conventional lithium-ion secondary batteries using carbon materials as negative electrodes face issues with lithium deposition during rapid charging at low temperatures, leading to internal short-circuits and capacity degradation, while oxide-type materials like lithium titanate offer improved characteristics but still generate excessive CO2 during high-temperature storage.

Innovation Solution

A negative-electrode active material with lithium titanate having a spinel structure, where the specific surface area and pH are optimized to satisfy the relationship B×P < 50, reducing CO2 generation during high-temperature storage by adjusting the surface state and removing base substances like lithium carbonate and hydroxide.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If carbon materials are used as negative electrode material, then high energy density is achieved, but lithium deposition occurs during rapid charging at low temperature

Engineering Contradiction:

Improveenergy densityVSAvoidlithium deposition resistance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent changes the operating potential parameter by using lithium titanate instead of carbon materials, shifting the lithium ion insertion/extraction potential from 0.1V to 1.5V vs Li/Li+. This parameter change eliminates lithium deposition while maintaining high energy density through optimized electrode composition and structure.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If lithium titanate is used as negative electrode material, then lithium deposition is prevented, but CO2 generation occurs during high temperature storage

Engineering Contradiction:

Improvelithium deposition resistanceVSAvoidCO2 generation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by creating a hydrophobic coating layer on the surface of lithium titanate particles. This localized modification reduces the reactive surface area that contacts electrolyte and generates CO2, while the bulk material maintains its excellent lithium ion insertion/extraction properties. The hydrophobic layer acts as a barrier that suppresses harmful side reactions during high temperature storage.

Inventive Principle:

Principle #3Local quality

3Productivity

If lithium titanate with high specific surface area is used, then reaction activity is improved, but CO2 generation increases during storage

Engineering Contradiction:

Improvereaction activityVSAvoidCO2 generation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining lithium titanate with hydrophobic substances to form a core-shell structure. The lithium titanate core provides high reaction activity for lithium ion insertion/extraction, while the hydrophobic shell reduces CO2 generation during storage. This composite structure resolves the contradiction between reaction activity and storage stability.

Inventive Principle:

Principle #40Composite materials

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The optimized lithium titanate negative-electrode active material significantly reduces CO2 generation during high-temperature storage, enhancing the reliability and performance of lithium-ion secondary batteries by minimizing gas production and maintaining discharge output characteristics.

Implementation Method 1

lithium titanate is capable of reversibly occluding and releasing lithium ions

Methodology Applied

Scientific EffectIon insertion and extraction: Absorption (physical)

Implementation Method 2

B is a value (m2/g) representing a specific surface of the lithium titanate as measured by a BET technique

Methodology Applied

Scientific EffectGas adsorption: Adsorption

Implementation Method 3

P is a value obtained by immersing 1 g of a lithium titanate in 50 cm3 of redistilled water and determining a pH of the redistilled water

Methodology Applied

Scientific EffectpH measurement:

Data Source

PatentUS9287562B2Negative electrode active material comprising spinel lithium titanate, electrical storage device, and method for producing negative electrode active material

Publication Date: 2016.03.15 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A negative-electrode active material disclosed herein contains a lithium titanate having a spinel structure, and satisfies the relationship B×P<50, where B is a specific surface (unit: m2/g) of the lithium titanate as measured by a BET technique; and P is obtained by immersing 1 g of the lithium titanate in 50 cm3 of redistilled water and determining a pH of the redistilled water after 30 minutes of agitation.